Smart Window Optical Laminate With Hardness-Controlled Polarizer Layers

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Solution Overview

Problem

Conventional optical laminates for smart windows suffer from issues such as bubbles and black spots due to the direct compression of polarizing plates and transparent conductive layers during manufacturing, leading to mechanical weakness and fixed transmittance, which can cause glare or reduced visibility depending on ambient light conditions.

Innovation Solution

The optical laminate comprises first and second laminates with polarizing plates and transparent conductive layers, each having adjusted Martens hardness (100 N/mm² to 430 N/mm²) and elastic recovery rate (40% to 87%), allowing direct contact without a separate substrate, thereby minimizing defects and enabling smooth transmittance variation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If a composite layer is formed by bringing a polarizing plate and a transparent conductive layer into direct contact with each other without including a separate substrate, then the thickness of the transmittance variable optical laminate is reduced, but the mechanical properties and appearance quality deteriorate due to bubbles and black spots occurring during manufacturing

Engineering Contradiction:
Improvethickness of optical laminateVSAvoidappearance quality and mechanical properties
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the Martens hardness of the polarizing plate (100-400 N/mm²) and the pressing conditions (pressure, temperature, time) during manufacturing. By adjusting these parameters, the patent achieves optimal balance between reducing thickness and preventing defects like bubbles and black spots, allowing direct contact lamination without separate substrates while maintaining reliability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite structure by directly laminating the transparent conductive layer onto the polarizing plate surface, forming an integrated composite layer. This composite material approach eliminates the need for separate substrate layers, reducing overall thickness while maintaining structural integrity through controlled bonding processes that prevent defect formation

Inventive Principle:
Principle #40Composite materials

2Object-affected harmful factors

If the overall transmittance is preset low to prevent glare during day, then glare is reduced, but visibility at night when ambient light is insufficient deteriorates

Engineering Contradiction:
Improveglare to driverVSAvoidvisibility at night
Core Design Contradiction:
Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The patent implements dynamics by making the optical laminate's transmittance variable rather than fixed. The laminate can dynamically adjust its light transmission properties in response to changing ambient light conditions, being transparent during the day to prevent glare and becoming more transmissive at night to improve visibility, thus adapting to different operational environments

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent applies parameter changes by enabling the optical laminate to change its transmittance parameter based on ambient light conditions. Through voltage application or other control mechanisms, the laminate transitions between different transmittance states, optimizing both glare prevention during the day and visibility at night by adjusting the optical properties as needed

Inventive Principle:
Principle #35Parameter changes

3Illumination intensity

If the overall transmittance is preset high to improve visibility at night, then visibility is improved, but glare to driver occurs during day when ambient light is sufficient

Engineering Contradiction:
Improvevisibility at nightVSAvoidglare to driver
Core Design Contradiction:
Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent implements dynamics by enabling the optical laminate to actively adjust its transmittance level based on real-time ambient light detection. During the day, the laminate maintains low transmittance to prevent glare, while at night it increases transmittance to improve visibility, thus dynamically optimizing both safety parameters throughout the operating cycle

Inventive Principle:
Principle #15Dynamics

Data Source

PatentEP4670969A1Optical laminate and smart window including the same
Publication Date: 2025.12.31 DONGWOO FINE CHEM CO LTD
  • EP4670969A1 patent drawingFigure 1~2
  • EP4670969A1 patent drawingFigure 3a~3b
  • EP4670969A1 patent drawingFigure 4a~4d

AI summary

Disclosed is an optical laminate including: a first laminate comprising a first polarizing plate and a first transparent conductive layer; a second laminate opposite to the first laminate and comprising a second polarizing plate and a second transparent conductive layer; and a liquid crystal layer disposed between the first laminate and the second laminate, wherein the first laminate and the second laminate each has a Martens hardness (HM) of 100 N/mm2 to 430 N/mm2 and an elastic recovery rate (nIT) of 40% to 87%, as measured when a pressing load of 1 mN is applied thereto for 15 seconds using a nanoindenter. Also disclosed is a smart window including the optical laminate. A polarizing plate-transparent conductive layer laminate positioned above and below the liquid crystal layer is not deformed due to its excellent hardness and may be recovered after being compressed, due to its excellent elastic recovery rate.